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Pentium 1 motherboard questions.

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First post, by Baoran

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I recently bought a pentium 1 pc and it has this motherboard:

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It seems to have a brown cache slot. Does that mean that the cache chips on the motherboard are fake?
I also have had this cache module for quite some time. I don't remember where I got it.

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Is the cache module compatible with the brown slot that way that it would not fry anything?
Would installing the module improve performance of the PC in any way?

The motherboard has 80MB of ram but I read somewhere that the chipset on the motherboard only supports caching up to 64MB. Would it be better not to have 80MB of ram?

Reply 1 of 20, by Doornkaat

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The slot is for 256KB extra cache expansion. It expands the working onboard cache.
There is a standard for the COAST modules. Usually manufacturers adhere to it. I can't say wether your board and COAST does.

Reply 3 of 20, by Baoran

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Thanks. I found that earlier and I also found a manual at https://www.elhvb.com/mobokive/archive/Tmc%20 … al/AI5TV13D.PDF even though both are for different version of the motherboard since mine doesn't have usb headers and mine only has 4 memory slots.

It doesn't really answer my questions questions though. I think my module is 512KB and if those cache chips on the motherboard are real the motherboard already has 256KB, so I don't know if it is a good idea to try the module. Also it does not answer if the module would happen to work if it would actually improve performance. It would be also nice to find out if it would be better to reduce the amount of ram the motherboard like I asked in my first post.

Reply 4 of 20, by Horun

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Baoran wrote on 2020-10-17, 19:20:

Thanks. I found that earlier and I also found a manual at https://www.elhvb.com/mobokive/archive/Tmc%20 … al/AI5TV13D.PDF even though both are for different version of the motherboard since mine doesn't have usb headers and mine only has 4 memory slots.

It doesn't really answer my questions questions though. I think my module is 512KB and if those cache chips on the motherboard are real the motherboard already has 256KB, so I don't know if it is a good idea to try the module. Also it does not answer if the module would happen to work if it would actually improve performance. It would be also nice to find out if it would be better to reduce the amount of ram the motherboard like I asked in my first post.

Right ! The board has 256k (based on the cache two chips) but was designed to have either 256k or 512k. Either with 4 on board chips or 2 onboard + 256k COAST.
"L2 CacheSize: 256K or 512K Type: Pipelined Burst Synchronous SRAM onboard or Module"
Do not try the 512k COAST ! Without unsoldering the W9 and W10 hard-wired jumpers for "Onboard cache Enabled" you cannot disable the onboard cache.
If the board runs well I would hunt for a proper 256k COAST and NOT try to modify anything....
edit: fixed my bad grammar 😀

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 5 of 20, by Baoran

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Horun wrote on 2020-10-17, 19:56:
Right ! The board has 256k (based on the cache two chips) but was designed to have either 256k or 512k. Either with 4 on board […]
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Baoran wrote on 2020-10-17, 19:20:

Thanks. I found that earlier and I also found a manual at https://www.elhvb.com/mobokive/archive/Tmc%20 … al/AI5TV13D.PDF even though both are for different version of the motherboard since mine doesn't have usb headers and mine only has 4 memory slots.

It doesn't really answer my questions questions though. I think my module is 512KB and if those cache chips on the motherboard are real the motherboard already has 256KB, so I don't know if it is a good idea to try the module. Also it does not answer if the module would happen to work if it would actually improve performance. It would be also nice to find out if it would be better to reduce the amount of ram the motherboard like I asked in my first post.

Right ! The board has 256k (based on the cache two chips) but was designed to have either 256k or 512k. Either with 4 on board chips or 2 onboard + 256k COAST.
"L2 CacheSize: 256K or 512K Type: Pipelined Burst Synchronous SRAM onboard or Module"
Do not try the 512k COAST ! Without unsoldering the W9 and W10 hard-wired jumpers for "Onboard cache Enabled" you cannot disable the onboard cache.
If the board runs well I would hunt for a proper 256k COAST and NOT try to modify anything....
edit: fixed my bad grammar 😀

I kind of went ahead of myself and installed the module before I read your message. I thought that I really didn't have any other motherboard to use it with. Luckily nothing bad happened. I used pause key on the keyboard to pause the screen when it shows the table of all information before it starts loading windows and it shows 256KB without the module and 512KB with the module. It is a 512KB module because it has those UMC memory chips that you see on the picture on both sides of the board. Main issue with the module is that the motherboard does not fit inside the case if the module is installed. It hits the hard drive cage.

Main question is now: Does it affect performance at all if I use 256KB or 512KB of cache with this motherboard? If it does not change anything I don't need to worry about the module not fitting inside the case. If it matters I could consider putting the motherboard to a different case. Also if the cacheable amount is 64MB, would it be better to reduce the memory amount to 64MB?

Reply 6 of 20, by mpe

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Baoran wrote on 2020-10-17, 20:08:

Main question is now: Does it affect performance at all if I use 256KB or 512KB of cache with this motherboard? If it does not change anything I don't need to worry about the module not fitting inside the case. If it matters I could consider putting the motherboard to a different case. Also if the cacheable amount is 64MB, would it be better to reduce the memory amount to 64MB?

512kB is going to give you small 1-3% performance boost compared to 256k, depending on application.

Unless you are running a software that doesn't fit to 64MB and benefits from extra 80MB, it is better to reduce your RAM to 64M to make sure it is fully cached.

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Reply 7 of 20, by Baoran

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mpe wrote on 2020-10-17, 20:20:
Baoran wrote on 2020-10-17, 20:08:

Main question is now: Does it affect performance at all if I use 256KB or 512KB of cache with this motherboard? If it does not change anything I don't need to worry about the module not fitting inside the case. If it matters I could consider putting the motherboard to a different case. Also if the cacheable amount is 64MB, would it be better to reduce the memory amount to 64MB?

512kB is going to give you small 1-3% performance boost compared to 256k, depending on application.

Unless you are running a software that doesn't fit to 64MB and benefits from extra 80MB, it is better to reduce your RAM to 64M to make sure it is fully cached.

Would that performance boost matter much in games? I was considering installing either sound blaster CT2800 or CT4520 isa card and a voodoo 1 4MB card in it.

Edit: If it matters I could also replace the 100Mhz cpu with 120Mhz one I have somewhere.

Reply 8 of 20, by Horun

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More than 256k Cache does not help most games in my experience, as long as all the memory is cached you are in the sweet spot. You will gain some going to a P120 from a P100 (but not as much as going to a P133) due to the P120 PCI bus will run at 30Mhz versus 33Mhz for P100 or P133. So you gain about 20% in CPU speed with a 120 but can loose 10% PCI (Video) speed....

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 9 of 20, by Baoran

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Horun wrote on 2020-10-17, 22:55:

More than 256k Cache does not help most games in my experience, as long as all the memory is cached you are in the sweet spot. You will gain some going to a P120 from a P100 (but not as much as going to a P133) due to the P120 PCI bus will run at 30Mhz versus 33Mhz for P100 or P133. So you gain about 20% in CPU speed with a 120 but can loose 10% PCI (Video) speed....

Could you run P120 with 33Mhz pci bus speed usually or would I need better cooling for that?

Reply 10 of 20, by mpe

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The P120 with Intel chipset will run PCI at 30 MHz which isn't a big loss.

However, I am yet to see a P120 that wouldn't run at 133 MHz...

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Reply 11 of 20, by Horun

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mpe wrote on 2020-10-17, 23:26:

The P120 with Intel chipset will run PCI at 30 MHz which isn't a big loss.

However, I am yet to see a P120 that wouldn't run at 133 MHz...

Agree ! Most all P120 will run fine at 133 Mhz (33mHz bus) as long as the heatsink and fan are of good quality. The more metal on the heatsink the better if OC'ing !

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 12 of 20, by Baoran

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mpe wrote on 2020-10-17, 23:26:

The P120 with Intel chipset will run PCI at 30 MHz which isn't a big loss.

However, I am yet to see a P120 that wouldn't run at 133 MHz...

Do you mean that with intel chipset even if I would set the dip switches for 133Mhz it would still be running at 120Mhz?

Reply 13 of 20, by Horun

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Baoran wrote on 2020-10-18, 01:30:

Do you mean that with intel chipset even if I would set the dip switches for 133Mhz it would still be running at 120Mhz?

NO it would run at 133Mhz, Pentiums are not clock locked, just multiplier locked. The P120 runs 4x at 30Mhz, if you increase clock to 33Mhz it will run at 133Mhz....hope that explains it

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 14 of 20, by Baoran

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Horun wrote on 2020-10-18, 02:28:
Baoran wrote on 2020-10-18, 01:30:

Do you mean that with intel chipset even if I would set the dip switches for 133Mhz it would still be running at 120Mhz?

NO it would run at 133Mhz, Pentiums are not clock locked, just multiplier locked. The P120 runs 4x at 30Mhz, if you increase clock to 33Mhz it will run at 133Mhz....hope that explains it

Thanks. I just misunderstood what he said. To me it sounded like it is the chipset that forces it to run at 120Mhz.

Reply 15 of 20, by Doornkaat

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Horun wrote on 2020-10-18, 02:28:
Baoran wrote on 2020-10-18, 01:30:

Do you mean that with intel chipset even if I would set the dip switches for 133Mhz it would still be running at 120Mhz?

NO it would run at 133Mhz, Pentiums are not clock locked, just multiplier locked. The P120 runs 4x at 30Mhz, if you increase clock to 33Mhz it will run at 133Mhz....hope that explains it

I don't think Pentium CPUs are multiplier locked. I have a Pentium 75 that'll run at 133MHz if I set the jumpers for a Pentium 133.
Maybe on some models not all multipliers are avaliable?
Edit: The official fsb are also 50, 60 and 66MHz making a Pentium 120 and 133 use a 2x multi while the 75, 90 and 100MHz models run at a 1.5x multi. I don't think any non-MMX Pentium has a 4x multiplier avaliable.
With Intel Socket 5/7 chipsets there's usually a fixed PCI divider of 1/2 making the PCI bus run at 25, 30 and 33MHz respectively.

Last edited by Doornkaat on 2020-10-18, 04:25. Edited 1 time in total.

Reply 16 of 20, by Horun

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Doornkaat wrote on 2020-10-18, 03:56:
Horun wrote on 2020-10-18, 02:28:
Baoran wrote on 2020-10-18, 01:30:

Do you mean that with intel chipset even if I would set the dip switches for 133Mhz it would still be running at 120Mhz?

NO it would run at 133Mhz, Pentiums are not clock locked, just multiplier locked. The P120 runs 4x at 30Mhz, if you increase clock to 33Mhz it will run at 133Mhz....hope that explains it

I don't think Pentium CPUs are multiplier locked. I have a Pentium 75 that'll run at 133MHz if I set the jumpers for a Pentium 133.
Maybe on some models not all multipliers are avaliable?

Thanks ! Yes, think you are correct, been a long day. Most MMX do have locked or translated multipliers but most standard do not iirc, think am confusing older Pentiums with newer MMX types.
Really need a day off... worked 13 out of the last 14 days and am getting burned out.

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 18 of 20, by Tetrium

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Horun wrote on 2020-10-18, 04:23:
Doornkaat wrote on 2020-10-18, 03:56:
Horun wrote on 2020-10-18, 02:28:

NO it would run at 133Mhz, Pentiums are not clock locked, just multiplier locked. The P120 runs 4x at 30Mhz, if you increase clock to 33Mhz it will run at 133Mhz....hope that explains it

I don't think Pentium CPUs are multiplier locked. I have a Pentium 75 that'll run at 133MHz if I set the jumpers for a Pentium 133.
Maybe on some models not all multipliers are avaliable?

Thanks ! Yes, think you are correct, been a long day. Most MMX do have locked or translated multipliers but most standard do not iirc, think am confusing older Pentiums with newer MMX types.
Really need a day off... worked 13 out of the last 14 days and am getting burned out.

Most Pentium MMX CPUs are actually not multiplier locked. At one time I tested virtually all my Pentium MMX CPUs 166MHz and 200MHz and only the later ones had only (some of) their higher multipliers locked.
What do you mean with translated multipliers? I assume you mean that a CPU will seem to interpret a certain multiplier for a different multiplier? If so, then this is caused by some of the multiplier settings having been disabled on the CPU so the motherboard settings for that BF pin doesn't affect the multiplier anymore (which is basically how they locked the higher multiplier afaik).
Iiuc it's mostly the Overdrive chips that are locked, but I'm not 100% certain about that.

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Reply 19 of 20, by dionb

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Tetrium wrote on 2020-10-18, 11:35:
[...] […]
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[...]

Most Pentium MMX CPUs are actually not multiplier locked. At one time I tested virtually all my Pentium MMX CPUs 166MHz and 200MHz and only the later ones had only (some of) their higher multipliers locked.
What do you mean with translated multipliers? I assume you mean that a CPU will seem to interpret a certain multiplier for a different multiplier? If so, then this is caused by some of the multiplier settings having been disabled on the CPU so the motherboard settings for that BF pin doesn't affect the multiplier anymore (which is basically how they locked the higher multiplier afaik).
Iiuc it's mostly the Overdrive chips that are locked, but I'm not 100% certain about that.

Translated multiplier: P55C (Pentium MMX) interprets 1.5x (BF0 and BF1 both high) as 3.5x. So you can't set one of these CPUs to lower than 2x (BF0 low, BF1 high) whatever bus you are running.

K6-2 CXT core does the same with 2x, interpreting it as 6x, so the lowest multiplier you can set there is 2.5x (BF0 and BF1 both low, BF2 high/floating)